www.Findagrave.com is not hard to use. It is a free site but to use it to post, just create a free account, create a "user name"- mine is my initials, and you're set to go. If you add to another gravesite, just double-check the long sets of digits twice. One error puts the information on the wrong grave... For military veterans, you can also add their service information and/or biography.
Just be careful of YEAR DATES. I've come across two where the bodies were returned after the war- WWII - and the person filling out the headstone dates put the wrong year. In both cases, the Illinois govt employee put 1945 for the death date - and both of the men were killed at Normandy on 6 June, 1944! Since it is literally "engraved in stone" all one can do is ignore the error, and Yes, I had copies of the headstone cards saying 1944
Just remember that the unmarked veteran's graves deserve whatever one can do to remember them.